Administrators of sites using the popular blogging platform WordPress face a new challenge: hackers are launching coordinated brute-force attacks on the administration panels of WordPress sites via unsecured home routers, according to a report on Bleeping Computer.

Once they’ve gained access, the attackers can guess the password for the page and commandeer the account.

The home routers are corralled into a network which disseminates the brute-force attack to thousands of IP addresses negotiating around firewalls and blacklists, the report stated.

The flaw was detected by WordFence, a firm that offers a security plugin for the WordPress platform. The campaign is exploiting security bugs in the TR-069 router management protocol to highjack devices. Attackers gain entry by sending malicious requests to a router’s 7547 port.

The miscreants behind the campaign are playing it low-key to avoid detection, attempting only a few guesses at passwords for each router.

While the exact size of the botnet is unknown, WordFence reported that nearly seven percent of all the brute-force attacks on WordPress sites last month arrived from home routers with port 7547 exposed to the internet.

The flaw is exacerbated by the fact that most home users lack the technical know-how to limit access to their router’s 7547 port. In some cases, the devices do not allow the shuttering of the port.

A more practical solution is offered by WordFence: ISPs should filter out traffic on their network coming from the public internet that is targeting port 7547.

“The routers we have identified that are attacking WordPress sites are suffering from a vulnerability that has been around since 2014 when CheckPoint disclosed it,” Mark Maunder, CEO of WordFence CEO, told SC Media on Wednesday.

The specific vulnerability, he pointed out, is the “misfortune cookie” vulnerability. “ISPs have known about this vulnerability for some time and they have not updated the routers that have been hacked, leaving their customers vulnerable. So, this is not a case of an attacker continuously evolving a technique to infect routers. This is a case of opportunistic infection of a large number of devices that have a severe vulnerability that has been known about for some time, but has never been patched.”

There are two attacks, Maunder told SC. The first is the router that is infected through the misfortune cookie exploit. The other is the attacks his firm is seeing on WordPress sites that are originating from infected ISP routers on home networks.

“The routers appear to be running a vulnerable version of Allegro RomPager version 4.07,” Maunders said. “In CheckPoint’s original 2014 disclosure of this vulnerability they specifically note that 4.07 is the worst affected version of RomPager. So there is nothing new or innovative about this exploit, it is simply going after ISP routers that have a large and easy to hit target painted on them.”

The real story here, said Maunder, is that a number of large ISPs, several of them state owned, have gone a few years without patching their customer routers and their customers and the online community are now paying the price. “Customer home networks are now exposed to attackers and the online community is seeing their websites attacked. I expect we will see several large DDoS attacks originating from these routers this year.”